1. Field of the Invention.
The present invention relates to composite waterproofing sheets which include a multiple layer assembly having a water impervious sheet or membrane forming a base layer, a layer of particulate material overlying the base layer, and a covering of a water permeable material such as a non-woven or woven fabric.
2. Description of the Prior Art.
U.S. Pat. No. 4,693,923 shows a water barrier product that has a water impervious sheet to which a layer of particulate material, such as sodium montmorillonite, which swells in the presence of a liquid, is adhered.
The layer of particulate material has to be formed so that it remains generally in the layer, and can be attached to the backing sheet in any desired manner.